Thousands of deaf people have benefitted from cochlear implantation. Yet, there is still a great need for continuing research to improve the performance of the cochlear implants so that as many patients as possible may receive maximum benefit. When speech signals are processed in a similar manner to the speech processors of the cochlear implants and the outputs are presented to normal-hearing subjects via loudspeakers, we can simulate the hearing with the cochlear implants. The proposed study is to use acoustic simulations of cochlear implants to study features of implant stimulation that are important for speech perception. Those features include number of electrodes, electrode location, low-pass cut- off frequencies for extracting signal envelopes, simulated insertion depth and spread of excitation, and speech-processing strategies. The proposed study will also define temporal and spectral features of implant stimulation that are important for a tonal language (specifically Mandarin Chinese). A tonal language differs from English in that the pitch or tonality of a monosyllable word conveys lexical meanings. Normal-hearing subjects will be required to perform speech discrimination and recognition tasks on processed speech signals. The understanding of stimulus features important for cochlear implants is essential to designs of future cochlear implants and to clinical fitting of cochlear implants. Our knowledge on how to process important speech feature such as tones for cochlear implants will lead to the development of cochlear implants for tonal languages and thus benefit millions of deaf people around the world.